The present invention relates a driveshaft fabricating machine which is capable of straightening, welding, and balancing driveshaft assemblies without necessitating removal of the workpiece from the machine. The invention has particular application toward the fabrication of driveshafts which are composed of a shaft tube having pivoting universal joints positioned at each end.
Driveshaft fabrication generally requires six distinct procedures. These procedures include: (1) cutting the shaft tube to proper length; (2) installing tube fittings such as spline shafts or flange yokes by press-fit assembly; (3) measuring runout and straightening the unwelded workpiece; (4) welding the fittings to the shaft tube; (5) final measuring of runout and straightening of the workpiece to eliminate any weld-induced distortion; and (6) dynamic balancing. With the exception of the press-fit step of number (2), these operations all require rotation of the shaft or workpiece. Usually, a variety of machines are utilized to achieve each of the fabrication steps. For instance, tube cut off is accomplished through use of a hollow spindle lathe. The straightening step is accomplished by placing the workpiece in a straightener press which has a hydraulic ram member which presses against the workpiece to achieve radial alignment. The balancing operation requires a balancing machine having an intricate set-up of spindles, shafts and bearings to provide smooth high-speed rotation of the workpiece so that vibration sensors may pickup out of balance areas on the workpiece. The welding operation can be accomplished with any of the above machines, if the speed of rotation can be reduced and controlled sufficiently to provide a smooth weld bead between the tube shaft and the endpiece attached to the tube shaft.
It is desirable for enhancing manufacturing efficiency and time utilization to combine as many as the above-noted fabrication procedures as possible and perform a plurality of the steps on a single machine without need for additional set-ups. The most natural combination of operations would be welding and balancing since the welding may be readily performed with the balancer running at a rotational slow speed. In practice, however, it has been found to be necessary to straighten the workpiece after welding and before final balancing to remove any distortion produced by the weld stresses. Thus, if a balancer is used as a rotary welding fixture, the workpiece must still be removed from the machine for the straightening operation and replaced in the machine for balancing. The object of performing more than one fabricating operation on a single set-up is eluded. The workpiece must still be straightened prior to welding, removed from the straightening machine and placed in the balancing machine, welded, removed from the balancing machine and replaced in the straightening machine, and finally upon final straightening, replaced in the balancing machine for the balancing operation. This is undesirable.
It has also been found to be difficult to combine the straightening and balancing steps into a single machine. It is possible to equip the driveshaft balancer with the necessary sensors for measuring runout in the straightening process, however, because each runout measurement must be followed by requisite bending in a straightener press, such an adaptation still fails to reduce the number of set-ups required. The workpiece must be removed from the balancing machine and placed in a separate straightening press for the straightening operation because the fragile spindles and bearings of balancing machines as well as the machine bed, ways, and stanchions are not designed to withstand the high forces developed by a tube straightener press. Therefore, the straightener press must be a single dedicated machine separate from the balancer. Repeated loading and unloading of the workpiece between the balancer and the straightener press render the combination of a balancer and runout measurement impractical.
The present invention provides a unique machine which achieves the procedures of straightening, welding, straightening and balancing while the workpiece is set-up in a single machine. The present invention reduces the number of set-ups for the fabrication of a driveshaft from 6 to 3, namely: (1) tube cut off; (2) press-fitting; and (3) straightening, welding, straightening and balancing.